Recently, a chargeable-dischargeable battery is utilized as drive power sources of vehicles such as a hybrid car and an electric car or portable electronic devices such as a note-sized personal computer and a video camcorder. As a technique used for such a battery, for example, Patent Document 1 discloses a joining method of resistance-welding layered aluminum foils to a base plate made of aluminum. To be concrete, this joining method includes an ultrasonic tack welding step of forming a tack weld part in which a plurality of layered aluminum foils are tack welded by ultrasonic welding and a resistance welding step of resistance-welding the tack weld part to the base plate by clamping these tack weld part and base plate between two electrodes and then energizing the electrodes.